Characterization and preparation of oligomeric procyanidins from Litchi chinensis pericarp

The main purpose of this study is to characterize and prepare A-type oligomeric procyanidins from litchi pericarp (Litchi chinensis Baila). The variety of oligomeric procyanidins was characterized by LC–ESI–MS analysis. There were (+)-catechin, (−)-epicatechin, twelve dimers and six trimers of procyanidins were found in litchi pericarp extracts, and A-type procyanidins were much more abundant than B-type procyanidins. The main flavan-3-ol monomer and oligomeric procyanidins in litchi pericarp were (−)-epicatechin, A-type dimers (A1 and A2) and trimer (epicatechin-(4β-8, 2β-O-7)-epicatechin- (4β-8)-epicatechin). Procyanidin A1 (epicatechin-(4β-8, 2β-O-7)-catechin) was identified by NMR in litchi pericarp for the first time. (−)-Epicatechin and oligomeric procyanidins were prepared by the combination of AB-8 column chromatography and Toyopearl HW-40S column chromatography. The results showed that each fraction predominantly owned a single compound and gave a high yield with (−)-epicatechin, A-type dimers (A1 and A2) and trimer, suggesting a useful method to obtain pure (−)-epicatechin and A-type oligomeric procyanidins.

Graphical abstractWe characterized the main oligomeric procyanidins of litchi pericarp by LC–ESI–MS analysis and identified A1 (epicatechin-(4β-8, 2β-O-7)-catechin) by NMR for the first time in litchi pericarp. As the main compounds in litchi pericarp, (−)-epicatechin, A-type dimers (A1 and A2) and trimer (epicatechin-(4β-8, 2β-O-7)-epicatechin-(4β-8)-epicatechin) were prepared by the combination of AB-8 and Toyopearl HW-40S column chromatography.Figure optionsDownload full-size imageDownload high-quality image (115 K)Download as PowerPoint slide